Expand test coverage across server, agent, and web; fix bugs found during audit.

Adds hundreds of unit/integration/e2e tests, fixes WS bcrypt auth, config merge, fleet analytics, agent schedule/log tail, and documents stale PROBLEMS items. Updates PROBLEMS.md, README, and test scripts; ignores local spread-kits and coverage dirs.

agent/miner/pool.go

@@ -24,6 +24,10 @@ type Pool struct {
 
 	mu         sync.RWMutex
 	currentJob *job.Job
+	// jobGen is incremented atomically every time SetJob replaces the current job.
+	// Workers compare their local snapshot to detect job changes inside the inner
+	// hash loop without acquiring mu on every iteration.
+	jobGen     atomic.Uint64
 	stopCh     chan struct{}
 	wg         sync.WaitGroup
 	paused      atomic.Bool
@@ -62,16 +66,24 @@ func NewPool(threads int, cfg config.RuntimeConfig, reporter *stats.Reporter, ha
 
 func (p *Pool) SetJob(job *job.Job) {
 	p.mu.Lock()
-	defer p.mu.Unlock()
 	p.currentJob = job
+	// Bump generation while holding the write-lock so workers that check jobGen
+	// inside their inner batch loop break out and re-snapshot the new job.
+	gen := p.jobGen.Add(1)
+	_ = gen
 	if job == nil {
+		p.mu.Unlock()
 		return
 	}
 	seed := job.SeedHash
 	if seed == "" && len(job.Blob) >= 64 {
 		seed = job.Blob[:64]
 	}
-	for _, engine := range p.engines {
+	// Capture engines slice before releasing the lock.
+	engines := p.engines
+	p.mu.Unlock()
+	// Update all engines outside the pool lock — each Engine has its own mutex.
+	for _, engine := range engines {
 		if err := engine.SetJob(seed, job.Blob); err != nil {
 			log.Printf("[miner] failed to set job: %v", err)
 		}
@@ -202,6 +214,10 @@ func (p *Pool) worker(id int, engine *Engine) {
 			continue
 		}
 
+		// Snapshot the generation before the inner loop so we can detect a new
+		// job mid-batch and break early rather than hashing 256 stale nonces.
+		startGen := p.jobGen.Load()
+
 		for batch := 0; batch < 256; batch++ {
 			select {
 			case <-p.stopCh:
@@ -211,6 +227,10 @@ func (p *Pool) worker(id int, engine *Engine) {
 			if p.paused.Load() || p.remotePause.Load() {
 				break
 			}
+			// New job arrived — abandon this batch and re-snapshot immediately.
+			if p.jobGen.Load() != startGen {
+				break
+			}
 
 			hashHex, _, err := engine.HashAtNonce(nonce)
 			if err != nil {